very interesting. Another thing people do is relocate the O2 so that it is sticking straight up. This way its sampling the air at the 'top' of the exhaust pipe and not at the side. I guess the theory is that the heavy particulate junk that is in the exhaust is heavier than the air and falls to the bottom of the pipe as it travels through it. Moving the O2 to sample at the pipes highest point gets it out of that junk and into the air that needs to be measured.